Machine tools are generally known in practice, and specifically so-called travelling stand machines, which have a machine bed, on which an x-slide is displaceably arranged on x-guide rails. Arranged on the x-slide are z-guide rails extending in the z-direction, on which a z-slide is displaceably guided. The x-slide and the z-slide thus form a cross-slide. A stand, on the front side of which, facing a working chamber, a y-slide is vertically displaceably arranged on vertical y-guide rails, is arranged on the z-slide. A tool spindle which is non-displaceable in the z-direction relative to the y-slide, is rotationally drivable, extends in the z-direction and carries a tool holder on its end facing the working chamber, is attached to the y-slide. A workpiece holder is located in front of the spindle in the working chamber. The movements of the tool spindle and therefore of the tool held in the tool holder in the horizontal x- and z-directions take place due to corresponding displacement movements of the cross-slide with the stand. The vertical displacement movements take place by means of the y-slide. In these known machines, a tool magazine with a tool changer is located on one side of the stand, so access to the working chamber from the corresponding side is impaired; it is, however, sufficient that access to the working chamber between the stand and workpiece holder is possible from the opposing side.
It has already become known to arrange two stands that are coupled to one another on a machine bed. This leads to precision problems during machining because of heat expansions within the machine.
A machine tool is known from EP 1 285 721 B1, which, on a machine bed, has a pair of x-guide rails running in the x-direction, on which x-slides configured as stands are displaceably arranged. Each x-slide has, on its front side facing the working chamber, a vertically displaceable y-slide, on which a z-slide carrying a tool spindle is in turn arranged, so the tool spindle with a front tool holder can be displaced in the z-direction. Arranged above the upper sides of the x-slides configured as stands is a bridge, on which a tool magazine is arranged. The x-slides are constantly arranged below the bridge. The y-slides, on their front side, carry tool changers, which are moved upward for the tool change with the y-slide and the z-slide. As each z-slide has a quill-like configuration, the known machine tool is not intrinsically rigid. The problems outlined at the outset cannot be eliminated with this machine tool.